


Little Black Box

by Kahleniel



Category: Shingeki no Kyojin | Attack on Titan
Genre: Canon Universe, Eren Is a Little Shit, Exhibitionism, Fucking Machines, Levi Is In Denial, M/M, Masturbation, Multiple Orgasms, Nonbinary Hange Zoë, Not Canon Compliant, One Shot, Orgasm Control, Sensory Deprivation, Sex Toys, Voyeurism, non-binary hanji
Language: English
Status: Completed
Published: 2017-04-25
Updated: 2017-04-25
Packaged: 2018-10-23 21:41:01
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,919
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/10727802
Author URL: https://archiveofourown.org/users/Kahleniel/pseuds/Kahleniel
Summary: “Oi, Glasses, you in here?”“Over here, Levi!”Hanji’s voice came from one of their medical exam stations where the rhythmic whirring of machinery had been emanating since he stepped into Hanji’s lab.A long, low moan sounded out from behind the exam room curtain.“What the - Hanji, are you hiding another fucking titan back here?” Levi flung the curtain aside and reached for his knife he always kept tucked in his belt. What greeted him stopped him in his tracks.“Well...kinda?”





	Little Black Box

Captain Levi stormed down the long stone hallway, irritated to be sent as a glorified messenger boy on Erwin’s behalf to deliver a report to Hanji that they could have very well picked up themselves the next time they left their lab to come up for air. The combined laboratory and medical office was situated on the far end of the castle, on the same underground floor as the dungeons but at the opposite end of the building. Unlike the dungeons, however, the laboratory was relatively spacious and had several sets of small rectangular windows set along the wall forming the courtyard side of the castle. Levi was always surprised that no one ever reported hearing anything from beyond the windows, but they must have been specially designed at some point during the castle’s construction. In any case it was quiet, isolated, and kept Shitty Glasses from taking over the rest of the compound with their experiments, which made the lab perfect in his eyes.

He finally reached the laboratory and threw the door open, not bothering to knock. He knew that Hanji wouldn’t notice the noise anyway if they were absorbed in their work. He looked around the main part of the lab, but didn’t see them anywhere.

“Oi, Glasses, you in here?”

“Over here, Levi!”

Hanji’s voice came from one of their medical exam stations where the rhythmic whirring of machinery had been emanating since he stepped into Hanji’s lab.

A long, low moan sounded out from behind the exam room curtain.

“What the - Hanji, are you hiding another fucking titan back here?” Levi flung the curtain aside and reached for his knife he always kept tucked in his belt. What greeted him stopped him in his tracks.

“Well...kinda?”

Levi’s eyes widened as the shock set in, his body flushing with embarrassment and arousal so fierce it felt like all his blood had rushed straight south. On the padded exam table in front of him Eren was kneeling on all fours, a pair of headphones on his ears and a blindfold covering his eyes. Behind him a long metal pole thrust rhythmically, attached to a motorized wheel by another pole welded to the first at an angle. At the end of the pole nearest Eren, a thick realistic-looking silicone cock was locked firmly onto the end, slowly but repeatedly thrusting into Eren’s slicked entrance. As Levi stared, a trickle of clear fluid dripped from the head of Eren’s cock to join the puddle already gathered on the table’s surface, and Eren moaned again. “Levi. Fuck, _Levi._ ”

“He doesn’t know you’re here.” Levi started, having forgotten Hanji was standing beside him. They pointed to the set of headphones. “He has earplugs on underneath those. He said it helps him forget himself during the sessions.”

Levi’s head whipped toward them. “What do you mean, _sessions_? Is this some sort of shitty experiment, glasses?”

Hanji’s eyes lit up and they grinned. “Actually, yes. It began as simple viability testing to see whether titan shifters can produce offspring. I needed a sample from Eren, but he was too nervous to provide one the old-fashioned way. He said it was because the barracks were always occupied and the bathroom wasn’t private enough, but even when I offered to let him produce a viable sample in my lab he was still nervous. So, we put our heads together and came up with this. It’s worked even better than we imagined, especially for the subsequent endurance tests.”

Levi continued to stare at Eren as the attachment pounded into him. Judging from the sweat rolling down Eren’s shoulder blades and the mess underneath him it was clear that he had fucked himself to completion at least twice before Levi had arrived, and was well on his way to a third. He sat down heavily onto one of Hanji’s chairs, his knees too weak to hold up even Humanity’s Strongest. Levi squirmed with embarrassment as he realized just how fucking _hard_ he’d gotten underneath his uniform. He desperately wanted to strip off his trousers and stroke himself, right here, while watching Eren fuck his own brains out on the machine.

Hanji smirked at him. “You know, Eren told me once that if you ever came in during one of his sessions, you were free to watch. He said it was only fair since you helped with the experiment.”

Levi snorted. _Well, he’s certainly gotten past his shy stage._ “How the fuck did I help? I didn’t even know about it until just now.” He tried to sound indignant, but his normal stoicism failed him. Levi’s breathing sped up and lust threaded through his voice as he noticed Eren was now fucking back onto the machine, a steady stream of tiny whimpers and moans falling from his mouth with each roll of his hips.

“Remember that time I asked you to let me take a mold of your cock?” He nodded, remembering Hanji’s request. They’d been drinking more than usual that night, and he hadn’t thought much of it, having long gotten used to Hanji’s myriad unusual requests over the years. He’d promptly marched into his bathroom with the instructions and kit, wobbling only slightly as he shut the door. Ten minutes later he emerged victorious, reverse mold of his dick encased in a plastic tube.

“Yeah, that was a hell of a request, even for you. Wasn’t even gonna risk asking what you wanted it for after I sobered up. Just figured it would be for one of your shitty titan experiments.”

“Well, you’re not wrong.”

He leaned closer, taking a better look at the silicone cock pounding into Eren. A thrill sang through him when he realized it was basically his own cock pleasuring Eren so much. “ _Fuck._ ”

Hanji turned toward their work table and picked up a set of keys. “I need to step out for a moment. Will you watch over him until I get back? Make sure he doesn’t accidentally fall off the table and injure himself or something?”

Levi whipped his head around at them and narrowed his eyes in disbelief. He was torn between mortification at being caught so blatantly panting over another soldier in his squad and a growing awareness - and appreciation - that Hanji and Eren had set him up. Not that he was complaining. Nothing got him off harder than being allowed to watch someone else lose themselves in pleasure. He turned back to watch Eren and waved his hand at them in dismissal, trying and failing to sound bored with the idea. “Fine, go. I’ll keep an eye on him.”

Hanji leered. “I’m sure you will.”

“Shut up, Glasses.”

Levi locked the door behind them as they left the lab, shutting the curtains for good measure just in case they decided to peek through a window under the guise of another ‘experiment’. He pulled the chair closer to the exam table to get a better view of Eren on his hands and knees. He noticed a small rectangular control box in Eren’s left hand, his thumb resting on a dial. As he palmed his trapped arousal he watched as Eren slowly turned the knob with his thumb. The machine behind him sped up, thrusting faster. “Ohhh, fuck, _yessss,_ Levi!” Eren’s mouth was hanging open, pants and whines spilling forth. He flicked a switch next to the dial and the machine started vibrating. “Fuck, _fuck._ ” Eren had stopped moving his hips, letting the entire length of the silicone cock fuck into him as the flywheel turned.

 _He’s taking the -_ my _\- whole fucking cock. Jesus._ Levi’s own cock twitched hard in his trousers. He ground the heel of his palm against his throbbing length again and bucked, chasing the friction for just a moment to take the edge off the rising tension.

Moans and pleas spilled unbidden from Eren’s lips as Levi lost himself in a fantasy. Levi imagined pinning Eren against his office wall, one hand on his hips and another holding his wrists above his head as he drilled into him from behind. It was Levi’s favourite scene, the scout proving his worth to his Captain in ways that had nothing to do with turning into a titan.

He startled Levi when he started talking, voice shaking both from lust and the rhythm from the machine. “Am I a g-good boy, Captain? Do I f-feel good for you, sssir?”

Levi’s breath caught for a moment, barely biting back a whimper, but he found himself whispering to Eren as he exhaled. “Fuck, Eren, you’re such a good boy. Such a _good fucking boy_.”

Eren was taking the attachment as deep as he could, writhing on the table in pleasure. His cock leaked a steady puddle onto the surface below him, and his breathy moans were punctuated with each thrust of the machine. He had dropped to his forearms at some point, maneuvering his body to search for the perfect angle. Suddenly, the silicone toy thrust in just right against his prostate and he moaned Levi’s name again, long and loud.

Levi gripped the arms of the chair to anchor himself. Watching Eren was delicious torture, but he didn’t know if he could continue to stay seated if Eren kept going for much longer. He didn’t know where to focus, his eyes roaming from Eren’s flushed cheeks, to his mouth, down his body to his cock, and finally his ass. Every part of the soldier’s sculpted body was beautiful and a thready moan from him joined the litany streaming from Eren as he watched him turn the dial up again.

“ _Fuck_ , sir, I’m so c-close. Please, _please_ sir, let me come let me -” Eren’s hand flew to his cock and he rapidly stroked himself.

Levi growled a response, too far gone to care if anyone heard. “Yes, Eren, _yes_ , come for me. _That’s it_ , sweetheart, fucking come for me, Eren!”

Eren opened his mouth in a wordless cry as wave after wave of his orgasm ripped through him. More splashes of come joined the mess on the exam table until overstimulation threatened to turn pleasure to true pain. He scrabbled to turn the machine off, hitting the kill switch before pulling off the silicone cock and flopping boneless and sated onto his side.

Levi jerked back to reality as he realized that Eren was about to remove the blindfold and catch him sitting there, his rock hard arousal tenting the front of his uniform and panting as if he’d run a marathon. He sprang out of his seat and adjusted his cock so that the apron hid his bulge as best it could, then jerked the laboratory door open. Levi barely avoided knocking Hanji over as he rushed down the hallway to his quarters. If anyone thought to question why the Captain looked even more pissed off than usual his scowl kept them from asking.

Once he reached his quarters he slammed the door closed, locking and re-locking it to make doubly sure no one would come barging in before sagging against it. Levi quickly slipped out of his straps and stripped off his uniform enough to reach in and free himself, shoving his apron and trousers down to mid-thigh in his impatience. He was leaking almost as much as Eren had been. Levi wrapped his fingers around his length and stroked loosely, spreading the slick precome along his length as he closed his eyes and allowed himself to sink back into his fantasies. A pang of shame shot through him for a moment before he remembered Hanji had said that Eren had given his permission for him to watch well beforehand. _Though I’m doing much more than just watching at this point._

Levi released his own groan of pleasure as he brushed his thumb along the rim of his head, wishing desperately to know exactly what Eren had been fantasizing about the two of them. Images filled his mind of the soldier bent over Levi’s desk, impatient and begging for his cock, needy and writhing as he tried vainly to thrust himself back onto Levi while he held him in place. Levi fucked into his fist as he rubbed the tip of his cock with the palm of his other hand, closing his eyes and speeding his thrusts up to match the speed of Eren’s machine, feeding his fantasy even more.

It was no longer Eren on a table before him, but Eren in front of him, swallowing his thick cock all the way to the base as Levi fucked his mouth. He could almost see the soldier’s cheeky smile, watching Levi fall apart from between his Captain’s thighs as he sucked him down and nosed at his hair, proving that he was indeed swallowing Levi’s entire length. His fantasy blurred and shifted into Levi joining Eren on the exam table, fucking him with his own cock instead of a silicone substitute. A whimper escaped Levi as fantasy and memory mixed to drive his lust even higher, his cock as hard and wet as if he’d been edging himself for hours. He could feel his orgasm approaching and sank to his knees, one hand on the wooden floor for support as he worked his cock frantically. He could feel the release building from his toes upward as he held his orgasm back for as long as possible. One last vision of Eren begging to come tipped him over the edge, and he let loose a long groan as he came hard, ropes of come spilling over his hand and onto the floor of his quarters. Even the slightest movement sent aftershocks coursing through him as he slumped forward, chest heaving in exertion as he emptied onto the floor between his knees. “Fuck.” He looked down at the mess on the hardwood below him. “ _Fuck._ ” He prayed that no one had heard him through his door as he stood on wobbly legs to get his cleaning supplies, hitching up his trousers and hastily fixing his uniform before anyone knocked on the door.

Levi did his best to avoid Eren in the days following his visit to the lab. To Hanji’s credit, the most they ever let on was a quick grin the first time they’d visited his office after to hand over budgetary details Erwin had requested he tally for the next scouting mission. He had halfway expected them to nag him for some sort of perverted after-action report ‘for science’, but he was pleasantly surprised, and not a little relieved, at their discretion. Eren, however, seemed to appear everywhere Levi went. Even during mealtimes the soldier’s eyes seemed to follow him, full of unasked questions and a tiny bit of hurt.

It wasn’t until the fifth day after that Eren burst in through his office door, shutting and locking it behind him. Levi stood quickly, planting his hands on his desk in irritation at the interruption.

“What is it, Jaeger? And unlock my fucking door.”

“No, not until you tell me what I’ve fucked up so badly that you won’t even reprimand me for it.”

“Did you just disobey a direct order, soldier?”

Eren threw up his hands. “No. Yes. Wait -”

Levi’s eyes narrowed dangerously. “I don’t have time for your shit, Jaeger.”

“Captain, sir, just...give me two minutes of your time and then I’ll unlock the door and be out of your hair.”

Levi paused, caught by the memory of Eren pleading on the exam table, that same ‘sir’ spilling out from his lips. He knew he couldn’t avoid him any longer, and sat back down with a sigh. “Fine. Two minutes.”

The smile on Eren’s face was almost blinding as he stood in front of Levi’s desk at parade rest, his hands clasped together at his lower back. His eyes caught Levi’s and held them as he spoke, softly so no one outside could hear. “Sir, I know you were in the lab. Hanji told me.”

A flush of shame crept up Levi’s neck and face. Before he could open his mouth, Eren carried on. “Wait, sir, it’s ok. I’m glad you stayed to watch. It’s what I wanted.” He stepped closer to the desk, out of parade rest and into a much more uncertain posture, the set of his shoulders betraying his tension. “I hope you wanted it too.”

Levi stared at him. _When had Eren become so bold? Or had he always been like this and I’d never noticed?_ He cleared his throat and blinked. _Such boldness deserves to be rewarded._

“Sir?” Eren’s face started closing in on itself, the soldier interpreting Levi’s shocked silence as rejection.

“Yes.”

“What?”

“I said yes, Eren. Yes, I wanted it - still want it.”

“Oh.” The sheer amount of emotions that played across Eren’s face as he went from fear to shock to confusion and relief looked absolutely exhausting to Levi, but the smile that shone at the end left no room for misinterpretation. Eren reached into his pocket and drew out a small silver and black box. “In that case, sir, maybe next time _you_ can be in control.” He placed the box on Levi’s desk, then saluted and hurried out the door before the Captain could respond.

Levi sat in place, momentarily stunned, then leaned forward and picked up the box Eren had left. He smirked to himself as he realized it was the master control to the fucking machine. “Oh, Eren, you’ll find out just how much in control I like to be.”

**Author's Note:**

> I maaaayyyy do a sequel/second bit if enough people tell me they would like to see just what happens when Levi takes control. If you want to read it, please let me know below!
> 
> Edit: OMG you guys!! I did NOT expect this much love! I'm overwhelmed and humbled, and there will DEFINITELY be a sequel to this! <3 <3 <3 <3 Thank you so much!!!!


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